Ironman: Run a Marathon?
Question: I was planning on doing a big run focus in Jan-Feb and I was thinking of using an early season marathon as a goal to keep me motivated. The Napa valley marathon is March 1st. I know there is a significant recovery cost after a marathon...is it worth it? If you feel that this is worthwhile, a sub-3-hour marathon would be a very satisfying accomplishment for me, but only if it is something which is building towards the higher priority goal of a 9:14 Ironman thois spring.
Answer: There is not a compelling reason to do a marathon when training for an Ironman. But there are many reasons why you shouldn’t. You mentioned one – the necessary recovery afterwards which may last a month if you PR’ed. During this time you’d be losing running fitness (the WKO+ Performance Management chart confirms this). There’s also an increased risk of injury and a loss of focus on swimming and cycling. Trying to PR in a marathon makes it an A-priority race. Too many of your resources (time and energy) are shifted to running as a result. You're first and foremost a triathlete. And, besides, the pace you run in an Ironman is no where near the pace you run in a marathon PR-attempt.
You’d be much better served by training for a half marathon. One of the many upsides of this, one which I really like, is that you train faster than when training for a marathon. The key to training is not how much training you do, but how much quality there is in your training. This generally equates to the intensity of your training. Faster training means faster running. I like to have Ironman triathletes run fast in the late base period because in the build period the running becomes much slower being done at your goal IM pace, which you could do all day if you hadn’t just finished a 4k swim and 112-mile ride.